Britain’s Supreme Court rules Parliament must have a say on Brexit

LONDON — Britain’s Supreme Court ruled Tuesday that Prime Minister Theresa May must get Parliament to sign off before triggering Britain’s exit from the European Union.

The decision adds a significant hurdle to May’s promise to invoke Article 50 — the never-before-used mechanism for getting out of the European Union — by the end of March.

Most observers, however, do not expect the decision to derail the Brexit process, which was set in motion when the country voted for departure by a margin of 52-to-48 in a June referendum.

Despite most members of Parliament having opposed Brexit, the political costs of blocking it now are seen as high. At most, lawmakers will likely try to shape May’s negotiating strategy rather than attempt to stop her outright.

Once Britain triggers Article 50, it will have two years to negotiate the terms of its departure.

“The British people voted to leave the E.U., and the government will deliver on their verdict — triggering Article 50, as planned, by the end of March,” May’s office said in a statement issued within minutes of the court’s ruling. “Today’s ruling does nothing to change that.”

The Supreme Court’s decision turned on the question of whether the prime minister or Parliament should have the last word in deciding Britain’s status in the European bloc.